Lubricious detergent compositions



United States. Patent 3,275,561 LUBRICIOUS DETERGENT COMPOSHTIONS DavidJ. Pye, Walnut Creek, and Donald K. Peterson, Los Angeles, Calif.,assignors to The Dow Chemical Company, Midland, Mich, a corporation ofDelaware N0 Drawing. Filed Oct. 3, 1957, Ser. No. 687,866 2 Claims. (Ci.252-410) This invention is concerned with soap and detergentcompositions and the manufacture thereof and is particularly directed toimproved compositions for use on the skin and to a method for producingsuch compositions.

This application is a continuation-in-part of our copending application,Serial No. 644,457, filed March 7, 1957, now abandoned.

In the manufacture of soaps, detergent compositions, shaving creams andthe like and particularly those which are employed in contact with theskin, it is desirable to produce a product characterized by a qualitywhich may be called lubricity. This quality of lubricity is ofconsiderable importance from the cosmetic standpoint particularly withrespect to the hand, that is, with respect to the feeling experienced bythe user of the product. In the case of shaving soaps, the quality oflubricity is more concretely of interest in that a shaving soap, byproviding more lubricity, improves the cutting of the hair or heard withless tendency to nicking and cutting of the skin. Further, certainpowdered hand soaps currently marketed have failed to achieve wideacceptance for household use on the basis of the housewifes dislike forthe unpleasant feeling of such compositions on the skin.

It is an object of the present invention to provide an improved soapcomposition. It is a further object to provide improved soapcompositions characterized by a high degree of lubricity. Another objectis to provide an improved method for preparing the new compositions. Yetanother object is to provide shaving soap compositions which increasethe ease of shaving. Other objects will become apparent from thefollowing specification and claims.

In the present specification and claims, the term soap, unlessspecifically designated or modified is employed in the broad genericsense as inclusive of synthetic detergent compositions, shaving soaps,amine salts of long-chain fatty acids, such as triethanolamine oleate orlaurate, and the like as well as the true soaps prepared by thesaponification of animal or vegetable fats or oils or by the reaction ofalkalis with long-chain fatty acids.

In accordance with the present invention, it has been discovered thatthe incorporation in soaps of certain high molecular weight,water-soluble polymers of acrylamide results in improved lubricity ofthe soap in use and imparts a more pleasant feeling when the soapcomposition is applied on the skin. It is among the advantages of theinvention that, in addition to the improved lubricity qualities obtainedwith the new compositions, stiffer and more persistent foams frequentlyare produced.

In accordance with a further embodiment of the invention, it has beendiscovered that the incorporation of the high molecular weight polymersof acrylamide in the soap compositions is advantageously accomplished byemploying the dry acrylamide polymer in finely divided or pulverulentcondition in accomplishing its admixture with the other ingredients ofthe finished composition.

The term acrylamide polymer, as herein employed to designate thepolymers used in the practice of the invention, is inclusive ofhomopolymers of acrylamide and copolymers of acrylamide with up to about15 percent by weight of other suitable monomers such a methacrylamide,acrylic and methacrylic acids and the alkali metal salts and lower alkylesters thereof, vinyl chloride,

3,275,561 Patented Sept. 27, 1966 vinyl alkyl ethers and the like,provided each such copolymer is characterized by water-solubility andviscosity properties as set forth below. In the copolymers of acrylamidewith acrylic or methacrylic acid or their alkali metal salts, higherproportions of the second ingredient to the acrylamide ingredient may beemployed and the expression acrylamide polymer includes copolymers ofacrylamide with up to about 50 mole percent of acrylic or methacrylicacid or an alkali metal salt thereof.

Water-soluble acrylamide polymers are usually characterized by a greateror less degree of hydrolysis, i.e., contain some free carboxyl groups.This condition is dependent upon the method of manufacture of thepolymer, the presence or absence of acrylic or methacrylic acid in thestarting monomer mixture, and conditions of storage of the polymer. Thepolymer products appear to be equivalent whether the carboxyls resultfrom copolymerization of acrylamide with acrylic or methacrylic acid orfrom hydrolysis of amide or ester groups subsequent to polymerization.In the practice of the present invention, the operable polymers, asabove defined, are those having not more than about 50 percent ofcarboXyl moieties based on the total of carboxyl and carboxamidemoieties in the polymer.

The term percent hydrolysis as hereinafter employed refers to thepercent of ca-rboxamide groups in the homopolymer of acrylamide replacedby carboxyl groups, whether derived by actual hydrolysis of thehomopolymer or by copolymerization as set forth above,

The acrylamide polymers employed in the present invention are watersoluble and have a low degree of crosslinking. In order to obtain thedesired lubricity characteristics, it is critical to employ highmolecular weight acrylamide polymers, that is, polymers characterized bya viscosity of at least 4 centipoises for a 0.5 percent by weightsolution of the polymer in an aqueous 4 percent by weight sodiumchloride solution adjusted to a pH of 5 to 6 at a temperature of 25 C.,such viscosity being measured with an Ostwald viscosimeter. When theacrylamide polymer contains carboxyl groups corresponding to over about10 percent hydrolysis, it is essential to determine the viscosity inaqueous sodium chloride solution at a pH of 5 to 6 and the termviscosity as employed in the following claims refers to the viscosity ofa 0.5 percent by weight solution of polymers determined under the aboveconditions. With acrylamide polymers containing carboxyl groupscorresponding to less than about 10 percent hydrolysis, the viscositycharacteristics may be determined on an aqueous 0.5 percent by weightsolution of the polymer in distilled water adjusted to a pH of 3 to 3.5at a temperature of 25 C. In either case, the minimum limitation of 4centipoises applies.

In the preparation of the compositions of the invention, it is essentialthat the acrylamide polymer be thoroughly .and intimately admixed withthe soap and other ingredients, if any, to produce a uniform finishedcomposition. In preparing certain of the compositions, particularlythose in which the finished composition contains sufiicient water or inwhich only minimal amounts of acrylamide polymer are to be introduced,it is convenient to employ the acrylamide polymer in the form of adilute aqueous solution. In such operations, the aqueous solution ofacrylamide polymer may be mixed with the liquefied soap in a crutcher orother mixing device. Alternatively, in soap and detergent compositionscontaining considerably more water than bar soap and powdered soapproducts, the acrylamide polymer may be dissolved in all or part of thewater employed in the formulation and thereafter blended with the otheringredients. The addition of the acrylamide polymers in the form ofaqueous solutions, however, is limited by the fact that such solutionsrapidly become more viscous with increasing concentration of acrylamdepolymer. Thus, for example, aqueous compositions containing 5 to percentby weight of the acrylamide polymers of the invention form highlyviscous solutions or rubbery gels which are extremely difficult to admixuniformly with other ingredients.

In an alternative and preferred mode of operation, the acrylamidepolymer in dry, finely divided form is intimately blended with the otheringredients to form the compositions of the invention. In one suchmethod of operation, bar soap is ground or flaked and mechanically mixedwith the dry, finely divided acrylamide polymer prior to milling andmolding into cakes. Alternatively, the dry, finely divided acrylamidepolymer may be mixed with the liquid soap or detergent in a crutcher orlike mixing device. In the latter mode of operation, it essential thatthe polymer be added portionwise with vigorous mixing in order toproduce a uniform composition. In a further mode of operation, theacrylamide polymer may be milled or otherwise thoroughly mixed with anydry builder or filler ingredients and the resulting finely divided solidcomposition be added to the soap or detergent in one of theabove-described methods of operation. Similarly, in the preparation ofpowdered soaps and detergents, the acrylamide polymer in finely dividedor powdered form is mechanically mixed with the other ingredients of thepowdered soap and sieved or ground as required to produce the desiredparticle size. The incorporation in the soap composition of theacrylamde polymer in dry, finely divided form, particularly when saidpolymer has been ground to pass a 100 mesh screen, constitutes apreferred embodiment of the invention. As herein employed, the meshscreen sizes refer to the Tyler Standard Screen Scale Sieves wherein ascreen of 100 meshes to the inch provide a sieve opening of about 0.147millimeter.

The amount of acrylamide polymer to be employed will vary depending uponthe type of soap or detergent ingredient used, the particular effectdesired in the finished soap product and upon the end use of suchproduct. In general, good results have been obtained when employing fromabout 0.1 to 4 percent by weight of acrylamide polymer based on thetotal weight of the soap composition. Amounts of from about 0.1 to 1percent by weight of acrylamide polymer are generally sufiicient incompositions based on true soaps whereas somewhat higher amounts of fromabout 0.5 to 4 percent by weight of acrylamide polymer are usuallyemployed in compositions based on synthetic detergents. The lubricityimparted to a soap composition is dependent upon the viscosity of thepolymer employed therein and generally increases with increasingviscosity. Thus, with high viscosity polymers, the desired hand of thesoap composition is achieved with smaller amounts of polymer than willbe required when employing a polymer characterized by a lower viscosity.

The acrylamide polymers employed in the present in vention may beprepared by known methods as, for example, by heating suitable solutionsof acrylamide monomer or of acrylamide monomer together with other suitable comonomers, as set forth above, in the presence of a free radicalinitiator such as an alkyl hydroperoxide or an alkali metal persulfate.The resulting acrylamide polymers may be subsequently modified byhydrolysis, if desired. Typical polymers adapted to be employed in theinvention are prepared as follows:

(1) P0lyacrylamide.100 grams of commercial acrylamide, containing about1 percent by weight of acrylic acid, and 0.5 gram of potassiumpersulfate are dissolved in 900 milliliters of water and heated atgradually in creasing temperature of from about 50 C. to about 90 C.during a period of 6 hours. The resulting highly viscous gel-likesolution of acrylamide polymer may be diluted with water for subsequentuse or dried on a drum drier to obtain the polymer product in dry flakeform. Typical polymers produced in this manner are characterized byviscosities of 4 to 10 centipoises for aqueous 0.5 percent 4 by weightsolutions thereof at pH 3 and at 25 C. Because of some hydrolysis duringthe polymerization, the product is found to be characterized byhydrolysis of from about 2 to 5 percent.

(2) P0lyac1ylamide.One-half gallon of an aqueous solution, containing 10percent by weight of purified acrylamide monomer at a pH of 5.2 ispurged of dissolved oxygen by bubbling purified nitrogen therethrough.0.5 milliliters of 2,2-bis-tertiarytbuylperoxybutane is then admixedwith the purged solution and the resulting mixture heated at atemperature of to C. under an atomsphere of nitrogen for eight hours.The resulting acrylamide polymer is characterized by hydrolysis of 1.6percent and by a viscosity of 7.2 centipoises for an aqueous 0.5 percentby weight solution thereof adjusted to a pH of 3 and a temperature of 25C.

(3) Acrylamide-methacrylamide copolymer.95 grams of acrylamide, 5 gramsof methacrylamide, 0.2 gram of potassium persulfate and 0.1 gram ofsodium bisulfite are dissolved in one liter of distilled Water and theresulting solution heated to 70 C. for 24 hours. The copolymer productis recovered by precipitation from the solution by the addition ofmethyl alcohol or by drying on a drum drier. In a similar fashion acopolymer of 92 percent acrylamide with 8 percent methacrylic acid isprepared.

(4) Aclylamide-acrylic acid copolymer.-An acrylamide polymer prepared asin (1) above has a degree of hydrolysis of about 5 percent and ischaracterized by a viscosity of 11.2 centipoises for a 0.5 percent byweight solution thereof in aqueous 4 percent sodium chloride solutionadjusted to a pH of 5 and a temperature of 25 C. 10 grams of thispolymer is dissolved in 480 milliliters of water, 0.7 gram of sodiumhydroxide dissolved in 10 milliliters of water is added thereto withstirring and the resulting mixture heated at 60 C. for 4 hours. There isobtained an acrylamide-acrylic acid copolymer, that is, an acrylamidepolymer characterized by about 18 percent hydrolysis. This polymer isfound to have a viscosity of 11.3 centipoises for a 0.5 percent byweight solution thereof in aqueous 4 percent by weight sodium chloridesolution adjusted to a pH of 5 and a temperature of 25 C.

The following examples illustrate the invention but are not to beconstrued as limiting the same.

Example 1 A shaving cream is prepared from the following ingredients:

In formulating the above composition, one-half the stearic acid ismelted in a corrosion-resistant kettle and the mineral oil is mixedtherewith. In another kettle, the potassium and sodium hydroxide aremixed and the borax and glycerine dissolved therein with stirring andheating. Into the resulting solution, the melted stearic acid is pouredwith vigorous agitation. Stirring is continued, with heating asrequired, for one-half hour to form a well blended saponified stearicacid mixture. Ihuring the above operation, the acrylamide polymer isdissolved in the water in a separate vessel with vigorous stirring andthe resulting solution combined with the coconut oil shampoo base. Theacrylamide polymer and coconut oil shampoo base mixture is heated andblended with the hot saponified stearic acid mixture and thereafter theremainder of the stearic acid is melted and mixed portionwise withvigorous stirring with the total mass. When the composition has beenthoroughly blended, a sample is withdrawn and analyzed for free fattyacid. If necessary, additional stearic acid or potassium hydroxide isadded as required by the analysis to adjust the free fatty acid contentto about 3 percent. Thereafter the mass is cooled to about 125 F. withconstant stirring and the 'witch hazel and perfume are added withcontinued stirring until the composition is smooth. The acrylamidepolymer employed is characterized by hydrolysis of 3 percent and aviscosity of 5 centipoises for a 0.5 percent by weight solution thereofin distilled water adjusted to a pH of 3 and a temperature of 25 C. Inuse, this composition is found to give a stable, small bubble latherhaving much better lubricity characteristics than an exactly similarcomposition without the acrylamide polymer ingredient.

Example 2 A dry powdered hand soap was prepared having the followingcomposition:

The soap consisted of about 20 percent coconut oil base sodium soaps andabout 75 percent tallow base sodium soaps. The acrylamide polymeremployed Was characterized by hydrolysis of about 3 percent and by aviscosity of about 9 centipoises for a 0.5 percent by weight solutionthereof in distilled Water adjusted to a pH of 3 and at 25 C. Theacrylamide polymer in flaked form was ground in a hammermill to finelydivided condition and mechanically mixed with the other ingredients.This formulation was found to have excellent cleansing and mild abrasiveproperties combined with a more pleasant soapy feeling on the skin thana similar composition without the acrylamide polymer ingredient.

Example 3 Commercial toilet soap (a blend of sodium soaps from naturalfats and oils) was ground and blended with varying amounts of anacrylamide polymer similar to that employed in Example 2. After thoroughmixing, each blend of soap and acrylamide polymer was reformed intocakes by pressing in a mold. A portion of the soap was milled in thesame fashion and repressed, without any addition of acrylamide polymer,to serve as a check. Evaluation indicated that the soap containing 1, 2and 4 percent by weight of acrylamide polymer had a soapier feel in useand produced a lather with smaller and stiffer bubbles. In home use by atest panel, a substantial majority of users preferred the soapcontaining 2 percent of acrylamide polymer as compared to the same soapwith no acrylamide polymer. As a result of the increased lubricity andstifier lather, the hand soap containing 2 percent of acrylamide polymerwas found to be excellent as a lather shaving soap. Any of the commonbar hand soaps of commerce can be substituted in the above formulationswith similar improved results.

Example 4 The following composition was prepared as a bubbleblowingsolution:

Potassium soap from coconut oil fatty acids 2 The acrylamide polymeremployed was characterized by hydrolysis of about 1.5 percent and aviscosity of 4 centipoises for an aqueous 0.5 percent by Weight solutionthereof at pH 3 and at 25 C. The household detergent contained 2 percentby Weight of sodium lauryl sulfate, 7 percent of sodium tallow alcoholsulfate, 9 percent of sodium dodecylbenzenesulfonate, 50 percent ofsodium tripolyphosphate, 0.5 percent of carboxymethylcellulose with thebalance perfume, dyes and inerts.

The acrylamide polymer was dissolved with vigorous stirring in the waterand the detergent and coconut oil soap thereafter added thereto withstirring. The resulting viscous composition was adapted to be employedwith childrens bubble-blowing devices to produce high-strength bubbleshaving remarkable persistence.

Example 5 Following the procedure of Example 2, compositions areprepared as follows:

Ingredient: Parts by weight Synthetic detergent 5-l0 Ground soap l530Borax 50-80 Acrylamide polymer 1-4 The compositions are used as mediumto heavy duty hand cleansers. Any of the acrylamide polymers, as aboveset forth, may be employed. The ground soap consists of sodium soapsderived from tallow or palm oil and coconut oil. Synthetic detergentssuch as sodium lauryl sulfate, sodium dodecylbenzenesulfonate, thesodium salt of sulfated coconut oil monoglyceride, nonyl phenyl ether ofa long-chain polyglycol or the like may be employed.

Example 6 An abrasive hand cleanser is prepared by blending thefollowing:

Ingredient: Parts by weight Sodium dodecylbenzenesulfonate 5.0 Tallowsodium soap 32.0 Coconut oil sodium soap 30.0 Lanolin 2L0 Diatomaceousearth 14.0 Pumice 8.0 Bentonite 4.0 Sodium metasilicate 3.5

Acrylamide polymer (dry, finely ground) 1.5

The acrylamide polymer employed is characterized by hydrolysis of 50percent and by a viscosity of 15 centipoises for a 0.5 percent by weightsolution thereof in aqueous 4 percent sodium chloride solution adjustedto a pH of 5 and a temperature of 25 C. The lanolin is melted andmechanically mixed with the dry, ground soap. The other ingredients arethen blended into the final composition and the latter is milled toprovide a dry, freefiowin-g powder.

Example 7 The base stock for a synthetic detergent bar soap contains 10percent of sodium tallow base soap, 5 percent of sodium coconut-oil basesoap, 74 percent of the sodium salt of sulfated coconut oilmonoglyceride, 1 percent of perfume and 10 percent of inerts. This basestock is heated in a blender and 1 percent by weight of dry, finelydivided acrylamide polymer, characterized by hydrolysis of 3.5 percentand a viscosity of 9 centipoises for a 0.5 percent by weight solutionthereof in distilled Water adjusted to a pH of 3 and a temperature of 25C. is added thereto portion Wise. After thorough blending of the aboveingredients, the mixture is milled, plodded and extruded in bar form toproduce a synthetic detergent bar which, in use, imparts a feeling ofimproved lubricity to the skin as compared to detergent bars preparedfrom the same base stock without the inclusion of the acrylamidepolymer.

Example 8 A sodium soap prepared by saponification of coconut oil is runinto a crutcher at a temperature of about 160 F. To each 80 parts byweight of this soap is added a mixture of 18.5 parts of finely groundpumice and 0.5 part of acrylamide polymer ground to pass a IOU-meshscreen of the Tyler Standard Sieve Series. Thereafter 1 part by weightof perfume is added and the resulting mixture is run into frames forcooling to prepare an abrasive bar soap having desirable lubricityproperties when used on the skin. The acrylamide polymer employed is apolyacrylamide characterized by hydrolysis of 6.2 percent and aviscosity of 8.5 centipoises for a 0.5 percent by weight solutionthereof in aqueous 4 percent sodium chloride solution adjusted to a pHof 5 and a temperature of 25 C. In use, this soap is found to give amore pleasant feeling of blandness and lubricity on the skin than anexactly similar abrasive bar soap without the acrylamide polymeringredient.

Example 9 20 grams of triethanolamine is dissolved in 474.7 grams ofwater and to the resulting solution 5 .3 grams of acrylamide polymer isadded with vigorous stirring. Stirring is continued for a period of timeto complete solution of the acrylamide polymer and 26.4 grams of stearicacid and 8 grams of hydroxypropyl-sucrose monomyristate added theretowith stirring. The resulting solution is placed in aerosol pressure cansand to each 90 parts by weight of said solution is added parts by weightof a mixture of 4 parts dichlorodifiuoromethane and 6 parts1,2-dichloro-1,1,2,2-tetrafluoroethane. The resulting aerosol shavecomposition produces a persistent lather having excellent lubricatingproperties on the skin. The acrylamide polymer employed was apolyacrylamide characterized by hydrolysis of about 6 percent and aviscosity of 5.8 centipoises for a 0.5 percent by weight solutionthereof in distilled water adjusted to a pH of 3 and a temperature of 25C.

A similar composition having desirable persistence and lubricity isprepared in exactly the same manner except that for the 5.3 grams ofacrylamide polymer in the above composition there is substituted 0.6gram of a polyacrylamide characterized by hydrolysis of about 4 percentand a viscosity of about centipoises for a 0.5 percent by weightsolution thereof in distilled water adjusted to a pH of 3 and atemperature of 25 C.

Example 10 A shampoo is prepared as follows:

Ingredient: Pounds Coconut oil 112 Potash lye, 38 Baum 83 Water 600Acrylamide polymer 5 Perfume 9 thoroughly blended with the filteredpotassium soap and glycerine at a temperature of about 160 F., theresulting mixture cooled to about 125 F. and the perfume added withcontinued stirring until the composition is homogeneous. The acrylamidepolymer employed is characterized by hydrolysis of 28 percent and by aviscosity of 13 centipoises for a 0.5 percent by weight solution thereofin aqueous 4 percent sodium chloride solution adjusted to a pH of 5 at atemperature of 25 C.

We claim:

1. A lubricious powered hand soap composition which consists essentiallyof from 50 to parts by weight of borax, from 15 to 30 parts by weight ofa ground soap consisting of the sodium salts of long-chain fatty acidsand from about 0.5 to 4 parts by weight of acrylamide polymer, saidpolymer being water-soluble and selected from the group consisting ofthe homopolymer of acrylamide, copolymers of acrylamide with up to about15 percent by weight of a member of the group consisting ofmethacrylamide, the lower 'alkyl esters of acrylic and methacrylicacids, vinyl chloride and vinyl alkyl ethers and copolymers ofacrylamide with up to about 50 mole percent of a member of the groupconsisting of acrylic and methacrylic acids and the alkali metal saltsthereof and said polymer being characterized by a viscosity of at leastabout 4 centipoises for a 0.5 percent by weight solution thereof inaqueous 4 percent by weight sodium chloride solution adjusted to a pH of5 to 6 and a temperature of 25 C.

2. A lubricious composition for the skin which consists essentially of amajor proportion of ingredients selected from the group consisting ofnon-soap anionic and nonionic synthetic organic detergents in intimatemixture with from about 0.1 to 4 percent by weight, based on the weightof the total composition, of an acrylamide polymer, said polymer beingwater-soluble and selected from the group consisting of the homopolymerof acrylamide, copolymers of acrylamide with up to about 15 percent byweight of a member of the group consisting of methacrylamide, the loweralkyl esters of acrylic and methacrylic acids, vinyl chloride and vinylalkyl ethers and copolymers of acrylamide with up to about 50 molepercent of a member of the group consisting of acrylic and methacrylicacids and the alkali metal salts thereof and said polymer beingcharacterized by a viscosity of at least about 4 centipoises for a 0.5percent by Weight solution thereof in aqueous 4 percent by weight sodiumchloride solution adjusted to a pH of 5 to 6 and a temperature of 25 C.

References Cited by the Examiner UNITED STATES PATENTS 1,976,679 10/1934Fikentscher et al. 260-89.7 2,781,320 2/1957 Jelinek et a1 252-12]2,805,205 9/1957 Touey et al. 252152 3,001,949 9/1961 Hansen 252-4533,130,166 4/1964 Schwalley 2521 10 OTHER REFERENCES Elder et al.: Drugand Cosmetic Industry, 77:5, November 1955, p. 714.

Smither: Washing, Cleaning, and Polishing Materials, Circular of theBureau of Standards, No. 383, Sept. 10, 1930, pp. 16, 18 and 19.

LEON D. ROSDOL, Primary Examiner.

JULIUS GREENWALD, Examiner.

A. T. MEYERS, Assistant Examiner.

1. A LUBRICIOUS POWERED HAND SOAP COMPOSITION WHICH CONSISTS ESSENTIALLYOF FROM 50 TO 80 PARTS BY WEIGHT OF BORAX, FROM 15 TO 30 PARTS BY WEIGHTOF A GROUND SOAP CONSISTING OF THE SODIUM SALTS OF LONG-CHAIN FATTYACIDS AND FROM ABOUT 0.5 TO 4 PARTS BY WEIGHT OF ACRYLAMIDE POLYMER,SAID POLYMER BEING WATER-SOLUBLE AND SELECTED FROM THE GROUP CONSISTINGOF THE HOMOPOLYMER OF ACRYLMIDE, COPOLYMERS OF ACRYLAMIDE WITH UP TOABOUT 15 PERCENT BY WEIGHT OF A MEMBER OF THE GROUP CONSISTING OFMETHACRYLAMIDE, THE LOWER ALKYL ESTER OF ACRYLIC AND METHACRYLIC ACIDS,VINYL CHLORIDE AND VINYL ALKYL ETHERS AND COPOLYMERS OF ACRYLAMIDE WITHUP TO ABOUT 50 MOLE PERCENT OF A MEMBER OF THE GROUP CONSISTING OFACRYLIC AND METHACRYLIC ACIDS AND THE ALKALI METAL SALTS THEREOF ANDSAID POLYMER BEING CHARACTERIZED BY A VISCOSITY OF AT LEAST ABOUT 4CENTIPOISES FOR A 0.5 PPERCENT BY WEIGHT SOLUTION THEREOF IN AQUEOUS 4PERCENT BY WEIGHT SODIUM CHLORIDE SOLUTION ADJUSTED TO A PH OF 5 TO 6AND A TEMPERATURE OF 25* C.